Submitted by hyh, also found by datapunk, Alex the Entreprenerd, and unforgiven
https://github.com/code-423n4/2022-06-illuminate/blob/912be2a90ded4a557f121fe565d12ec48d0c4684/marketplace/MarketPlace.sol#L131-L189
https://github.com/code-423n4/2022-06-illuminate/blob/912be2a90ded4a557f121fe565d12ec48d0c4684/lender/Lender.sol#L634-L657
Swapping function in Marketplace and Lenders yield() can be sandwiched as there is no slippage control option. Trades can happen at a manipulated price and end up receiving fewer tokens than current market price dictates.
Placing severity to be medium as those are system core operations, while funds there can be substantial, so sandwich attacks are often enough economically viable and thus probable, while they result in a partial fund loss.
All four swapping functions of Marketplace do not allow for slippage control:
https://github.com/code-423n4/2022-06-illuminate/blob/912be2a90ded4a557f121fe565d12ec48d0c4684/marketplace/MarketPlace.sol#L131-L189
Similarly, Lenders yield does the swapping without the ability to control the slippage:
https://github.com/code-423n4/2022-06-illuminate/blob/912be2a90ded4a557f121fe565d12ec48d0c4684/lender/Lender.sol#L634-L657
Consider adding minimum accepted return argument to the five mentioned functions and condition execution success on it so the caller can control for the realized slippage and sustain the sandwich attacks to an extent.
sourabhmarathe (Illuminate) confirmed 
